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37000 Feet | Browse and search NASA's Aviation Safety Reporting System |
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Widebody transport aircraft in cruise and on LNAV. Aircraft went off track when LNAV reverted to heading hold mode. ATC intervened alerting flight crew to course deviation.
| Attributes | |
| ACN | 390900 |
| Time | |
| Date | 199801 |
| Day | Sat |
| Local Time Of Day | 1801 To 2400 |
| Place | |
| Locale Reference | atc facility : czqm |
| State Reference | NB |
| Altitude | msl bound lower : 33000 msl bound upper : 33000 |
| Environment | |
| Flight Conditions | VMC |
| Light | Night |
| Aircraft 1 | |
| Operator | common carrier : air carrier |
| Make Model Name | Commercial Fixed Wing |
| Operating Under FAR Part | Part 121 |
| Navigation In Use | Other Other |
| Flight Phase | cruise other |
| Route In Use | enroute : other oceanic enroute : atlantic enroute airway : czqm |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | flight crew : first officer |
| Qualification | pilot : atp |
| Experience | flight time last 90 days : 200 flight time total : 8000 flight time type : 300 |
| ASRS Report | 390900 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| Qualification | pilot : atp |
| Experience | flight time last 90 days : 200 flight time total : 27000 flight time type : 2000 |
| ASRS Report | 381664 |
| Events | |
| Anomaly | aircraft equipment problem : less severe non adherence : clearance other anomaly other other spatial deviation |
| Independent Detector | other controllera |
| Resolutory Action | flight crew : returned to intended course or assigned course other |
| Consequence | Other |
| Supplementary | |
| Primary Problem | Aircraft |
| Air Traffic Incident | other |
Narrative:
Aircraft had been tracking the FMS flight plan route in LNAV for the past hour. Center called and asked our next fix on route of flight. We replied dophn. Center said we were slightly north of track. We then noticed LNAV had disengaged and we were apparently in heading hold mode. (Heading mode was not annunciated.) we immediately corrected back to track. We apparently were only a few mi off track. LNAV was re- engaged and tracked normally the rest of flight. We have no idea what caused the momentary LNAV disengagement.
Original NASA ASRS Text
Title: WDB ACFT IN CRUISE AND ON LNAV. ACFT WENT OFF TRACK WHEN LNAV REVERTED TO HEADING HOLD MODE. ATC INTERVENED ALERTING FLC TO COURSE DEV.
Narrative: ACFT HAD BEEN TRACKING THE FMS FLT PLAN RTE IN LNAV FOR THE PAST HR. CTR CALLED AND ASKED OUR NEXT FIX ON RTE OF FLT. WE REPLIED DOPHN. CTR SAID WE WERE SLIGHTLY N OF TRACK. WE THEN NOTICED LNAV HAD DISENGAGED AND WE WERE APPARENTLY IN HEADING HOLD MODE. (HEADING MODE WAS NOT ANNUNCIATED.) WE IMMEDIATELY CORRECTED BACK TO TRACK. WE APPARENTLY WERE ONLY A FEW MI OFF TRACK. LNAV WAS RE- ENGAGED AND TRACKED NORMALLY THE REST OF FLT. WE HAVE NO IDEA WHAT CAUSED THE MOMENTARY LNAV DISENGAGEMENT.
Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.